Previous research has shown that the presence of mild cognitive impairments (MCI) may increase the risk of the development of Alzheimer's disease in elderly individuals. The primary objective of this study is to determine whether high dose vitamin E or donepezil hydrochloride (Aricept) can delay a diagnosis of probable Alzheimer's disease (PRAD) in people with MCI. This three year long, multicenter, double-blind, placebo-controlled study will enroll 720 subjects in the United States and Canada. Efficacy will be determined by comparing the rate of conversion to PRAD for vitamin E or donepezil to that observed with placebo. The cognitive measures to evaluate efficacy of study drugs will be components of the neuropsychological battery, ADAS-cog and the MMSE. Global clinical functional change will also be measured in each group using various scales. All subjects will receive a multivitamin and will be randomized into one of the following conditions: donepezil, vitamin E, placebo. Nine visits will be conducted through a 3 year period. Subjects developing a diagnosis of PRAD during the study will be provided with donepezil at no cost for the remainder of the study. An intent-to-treat analysis will determine of there is a significant reduction in the hazard rate of conversion to PRAD in either of the treatment groups compared to placebo.